DESCRIPTION: There is still a need to develop new Dental monomers to overcome the shortcomings that limit the useable lifetime of resin based Dental restorations. Current day resin-based Dental composites have clinical performance deficiencies that include inadequate resistance to wear, secondary caries as a result of marginal leakage, and hydrolytic breakdown of filler-resin interface. Here it is proposed to correlate the chemical core structure of a polymerizable monomer to selected properties in the resulting Dental material. For example, dimethacrylate monomers with rigid aromatic and flexible aliphatic groups will result in polymers with increased toughness, a desired property for improving wear resistance in Dental composites. In this exploratory application we propose to synthesize aromatic acid monomers with varying numbers of rigid aromatic groups and flexible ether linkages interspaced between them. We will then study the influence of these chemical structures on the mechanical and physical properties of the resulting polymers (Aim 1). Analytical methods such as TLC, LC-MS, FTIR, NMR, and others will be used as necessary. Fracture toughness, conversion, water sorption and the viscoelastic properties and glass transition temperature of the polymers will be determined. Computer modeling of the monomers will be carried out to build an empirical correlation between the energy of rotation about the ether linkage and the resulting toughness of the polymer from the synthesized monomers (Aim 2). Molecular features such as the number and bulkiness of the aromatic groups can increase the energy of rotation due to steric hindrances and electronic interactions. The study will also include calculating the resulting energies from changing the ether linkage to e.g., a perfluoro-isopropylidene, carbonyl, or sulfone (-SO2-) group and others. This modeling may indicate which intramolecular features of the monomer are important for controlling the toughness of the polymer. The data gathered in these experiments will serve to support a larger R01 grant application with the long-term objectives of developing improved durable materials for adhesives and adhesive composites. [unreadable] [unreadable]